Detection by immunofluorescence of intracytoplasmic antigens in cell lines derived from human sarcomas

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Abstract
Fourteen cell lines originating from a variety of tumours of human connective tissue including osteosarcoma (6), fibrosarcoma (3), chondrosarcoma (2), rhabdomyosarcoma (1), Ewing's tumour (1) and chordoma (1) were maintained in tissue culture for variable periods ranging from 2 to 48 weeks. During their term in culture, acetone‐fixed monolayers of cells were serially subjected to indirect immunofluorescence (IF) tests using serum from cancer patients and individuals without malignancy, in an attempt to detect intracytoplasmic sarcoma‐associated antigens. Antigen‐positive cells were demonstrated in 10/14 cell lines, although their expression in tissue culture was variable, and cells exhibiting their IF features could not be unequivocally detected in the original tumour specimens. Such cells were present in cultures derived from sarcomas of different type (osteosarcoma, chondrosarcoma, fibrosarcoma, etc.) indicating the cross‐reactive nature of the antigens associated with them. The overall incidence of antibodies reactive with the cell lines in sarcoma patients in various phases of disease was 13/34 (38%) but antibodies were only occasionally detected in the sera of individuals without malignancy or with histologically unrelated neoplasms. Similar antigen‐positive cells could not be identified in 15 tissue cultures of comparable age in vitro originating from normal adult, carcinoma, or embryonic tissue or in seven long‐established cell lines, thereby implying a degree of specificity for sarcoma‐derived cell lines. The nature of the IF+ cells and of the antigen (s) expressed by them is discussed.